The great variability in the sonographic appearance of ovarian cystic teratomas poses difficulties for their diagnosis and classification. To overcome such difficulties, we have proposed a simplified classification of the pathognomonic echo patterns of ovarian cystic teratomas based on three basic types of echo pattern. In a prospective study of 118 echogenic adnexal masses, with postoperative histological confirmation, this classification enabled the correct diagnosis to be made in 115 cases (accuracy rate, 97.45%). In the three cases misdiagnosed preoperatively as ovarian cystic teratoma, the tumors proved to be benign and included a serous cyst adenoma, a serous cyst adenofibroma and a Brenner tumor. We suggest that, with our proposed classification of the echo patterns of ovarian cystic teratomas, sonography can become a quick and accurate tool in the recognition of this condition.